Hi Bodo, can you try starting Firefox in Safe Mode? After making sure Firefox is fully shut down, hold the Shift key when double-clicking the Firefox icon. You should see a dialog with several choices. Ignore those and click "Continue in Safe Mode." This will start Firefox with your add-ons disabled. If this runs correctly, I would suspect a problem with one or more of your add-ons. To disable all of them, you can close Firefox, restart in Safe Mode, and check the box to disable all your add-ons (first box only!). Then click Make Changes and Restart.

Does that make any difference? If so, you can re-enable your add-ons selectively starting with the most essential.

I looked up your crash ID, and the problem seems possibly related to malware. You may want to run some supplemental scans. These two tools are highly regarded:

Malwarebytes Anti-malware : http://www.malwarebytes.org/products/malwarebytes_free

SUPERAntiSpyware : http://www.superantispyware.com/